Some audio playback devices such as smartphones and tablets include amplifiers and speakers with limited output capabilities. In such devices, audio playback can be perceptibly distorted, and often acutely distorted, as playback level is increased during presentation. The characteristics of distortion are often frequency-dependent for a playback device. For example, a television cabinet may exhibit a resonance response at a specific frequency that is excited when an output signal at the specific frequency reaches or exceeds a particular level, resulting in an annoying rattle.
Multi-band compression can be applied to an audio signal before playback to reduce distortion and attempt to maximize playback level on a playback device. A distortion threshold is specified for each frequency band of the signal. The compressor applies an independent gain to each band to ensure that the signal level in each band does not exceed the corresponding distortion threshold.